Some communication networks apply congestion control mechanisms for mitigating traffic congestion in the network. For example, congestion control for Infiniband™ networks is specified in “InfiniBand Architecture Specification Volume 1,” release 1.2.1, Annex A10, November, 2007, pages 1650-1697, which is incorporated herein by reference. As another example, congestion control for Ethernet™ networks is specified in IEEE Standard 802.1Qau-2010, entitled “IEEE Standard for Local and Metropolitan Area Networks—Virtual Bridged Local Area Networks; Amendment 13: Congestion Notification,” Apr. 23, 2010, which is incorporated herein by reference.